Player pianos have been in common usage for many years. While player pianos differ in their general configuration, they usually function in substantially the same manner.
A typical player piano has a keyboard containing 88 keys similar to the keys of most other pianos. Above the keyboard of most player pianos is a mechanism which provides for the automatic operation of the piano. This mechanism in most player pianos employs a tracker bar in which is situated an array of pneumatic holes. Each hole corresponds to a single key of the keyboard.
The typical player piano control apparatus also includes two spindles which cooperate to hold the ends of a scroll so the center of the scroll is stretched tightly across the tracker bar. The scroll, which is often called a tape, is usually made of paper.
The typical player piano utilizes a source of power and interior mechanical parts which wind the scroll from one spindle to the other across the tracker bar at a predetermined speed and which also include a pneumatic system that applies suction to each tracker bar hole on the side opposite the paper scroll. The pneumatic system detects a pressure differential in the tracker bar holes to operate the piano keyboard action in a predetermined manner.
The player piano action is controlled by putting openings of predetermined size and length in the paper scroll so the openings cross the tracker bar holes in a predetermined manner.
When a paper scroll hole is aligned with a tracker bar hole the corresponding pneumatic system detects normal atmospheric pressure in the tracker bar hole. When a solid portion of the paper scroll covers a tracker bar hole, it prevents the passage of air through the tracker bar hole and the pneumatic mechanism therefore senses a different air pressure in the tracker bar hole than the level of air pressure existing therein when a hole in the paper scroll permits ambient air pressure surrounding the piano to communicate with the tracker bar hole.
Since the paper scroll more effectively seals the tracker bar hole when pressure in the tracker bar hole is less than the air pressure in the room around the piano, the pneumatic mechanism usually operates by applying suction to the tracker bar hole.
The aforedescribed paper scroll and player piano mechanics in operation are attractive in a nostalgic sense, but have certain inherent disadvantages. For example, the paper scroll can easily be torn or damaged. The paper scroll is also relatively bulky. The scroll drive mechanism requires maintenance, and the paper roll may tear.
It is therefore an object of this invention to replace the paper scroll by a valve board unit controlled by electric pulses which opens and closes the tracker bar holes in accordance with predetermined electric signals.
It is a further object of this invention to provide a valve board to replace a player piano paper scroll which connects directly to the face of a player piano tracker bar so as to open and close tracker bar holes at the same point they would be opened and closed by a paper scroll.
It is a further object of this invention to provide a valve board which can be premanently mounted on a player piano so as to control the player piano pneumatics while permitting conventional player piano operation controlled by a paper scroll.